Trip operating magnet



Feb. 14, 1956 B. G. TREMBLAY ET AL 2,735,046

TRIP OPERATING MAGNET I Filed Feb. 7, 1950 2 Sheets-Shee1 l ATTORNEY 2 Sheets-Sheet 2 bloy ond rn.

B. G. TREMBLAY ET Al- TRIP OPERATING MAGNET Feb. 14, 1956 Filed Feb. 7, 195o INVENTORS Bernard G..Trem MerIE.Ho BY #W W ATTORNEY United States Patent() TRIP OPERATING MAGNET Bernard G. Tremblay and Merl E. Horn, Pittsburgh, Pa.,

assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Application February 7, 1950, Serial No. 142,806 8 Claims. (Cl. 317-178) This invention relates to circuit breakers, and more particularly to circuit breakers of the type used to control light to moderate power distribution circuits.

Certain features disclosed but not claimed in this application are fully disclosed and claimed in copending application Serial No. 141,136, lled January 28, 1950, now Patent No. 2,669,623, February 16, 1954, by J'. B. MacNeill, F. E. Florschutz, T. Lindstrom and B. G. Tremblay and assigned to the assignee of the present invention.

An object of the invention is to provide a circuit breaker embodying an improved electromagnetic trip device provided with novel means for reducing eddy current losses.

Another object of the invention is to provide a circuit breaker having an electromagnetic trip device of mproved construction to provide a rigid structural support for the trip device and control elements therefor.

Another object of the invention is to provide a circuit breaker having an electromagnetic trip device embodying moving and stationary cores associated with a laminated magnetic circuit and supported by a rigid structural member in which the moving and stationary cores provide high resistance surfaces disposed at right angles to the direction of eddy current flow.

The novel features that are considered characteristic of the invention are set forth in the appended claims. The invention itself, however, both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description thereof, when read in conjunction with the accompanying drawings.

In said drawings:

Figure 1 is an elevational View, partly in section, of a circuit breaker embodying the principles of the invennon;

Fig. 2 is a fragmentary elevational sectional view showing one of the control valves for the time delay device and the adjusting means therefor, and

Fig. 3 is a vertical sectional view through the trip device and the time delay device therefor.

Fig. 4 is a horizontal sectional view in reduced scale taken on line lV-IV of Fig. 3 and looking in the direction indicated by the arrows.

Referring to Fig. 1 of the drawings, the circuit breaker includes a plurality of pole units each comprising a contact structure indicated generally at 11, and an overcurrent trip device indicated generally at 13. The contact structure and the trip device for each pole unit are mounted on a separate insulating base 15 which is rigidly secured to a metal supporting panel 17. Since the pole units are alike, only the center pole unit is illustrated and described herein.

The contactstructure 11 comprises stationary main and arcing contacts 19 and 21 both secured on the inner end of a terminal conducting bar 23, and cooperating movable main and arcing contacts 25 and 27. The movable contacts are rigidly secured to a contact carrying member 29 pivotally mounted by means of a pivot pin 31 on a U-shaped switch arm 33 which, in turn, is pivotally supported by pivot means 35 on brackets 37 rigidly mounted on the insulating base 15.

The movable contact carrying member 29 is electrically connected by means of a flexible conductor 39 to the energizing coil of the trip device 13. A spring 41 compressed between the movable contact carrying member 29 below its pivot 31 and the insulating base 15 provides contact pressure in the closed position of the breaker and also biases the movable contact structure in lopening direction.

The movable contact structure is normally maintained in the closed position by means of an operating mechanism indicated generally at 43 mounted in a U-shaped frame 45. The frame 45 is supported on a platform 47 which forms a cross member of a generally U-shaped main bracket comprising a pair of spaced side members 49 rigidly connected at their outer ends by the cross member or platform 47. The platform 47 extends substantially across the width of the breaker and the side members 49 are suitably secured to the metal panel 17 on the outside of the two outer pole units of the breaker.

The operating mechanism includes a lever 51 mounted on a pivot pin 53 supported in the side members of the frame 45. The lever 51 carries a rod 55 extending across all of the poles of the breaker and is connected by means of insulating connecting members 57 to the pivot pins 31 in the live ends of the switch arms 33 for the several poles of the breaker so that upon operation of the rod 55 the movable contacts of all of the poles move in unison.

An operating linkage comprising toggle links 59, 61 and 63 is provided to releasably hold the lever 51 and consequently the movable contacts in the closed position and to operate the movable contacts to open and closed positions. The toggle link 59 is pivotally connected to the lever 51 by means of a pivot pin 65 and the toggle link 63 is pivoted on a fixed pivot 67 supported in the frame 45. The toggle link 61 is pivotally connected to the links 59 and 63, respectively, by knee pivot pins 69 and 71.

The linkage 59, 61, 63 comprises two toggles, one of which 59-61 may be designated as the tripping toggle and the other 61-63 as the closing toggle. The tripping toggle 59-61 is normally slightly underset above a line drawn through the centers of the pivot pins 65-71 and the closing toggle 61-63 is normally underset below a line drawn through the centers of pivot pins 67-69. The closing toggle 61-63 is normally prevented from collapsing downward by a support member 73 pivoted on a pivot pin 75 supported in the frame 45 and having a shouldered portion engaging under the knee pivot pin 71.

The tripping toggle 59--61 is normally biased in a direction to cause its collapse by a component of the force of the springs 41 which bias the movable contact structures for the three poles of the breaker in opening direction and bias the connecting members 57 toward the left (Fig. 1). The tripping toggle 59-61 is normally prevented from collapsing by means of a main latch member 77 pivoted on the pin 53 and connected by means of a link 79 to the knee pin 69 of the tripping toggle.

The main latch member 77 is held in latching position by an intermediate latch lever 81 pivoted on the pin 75. The intermediate latch lever 8l carries at its upper end a latch roller 83 engaging the main latch 77 and at its lower end has a latching portion 85 normally engaging a latch member 87 on a channel-shaped latch 89 pivoted on a pivot pin 91 in the frame 45. A spring 93 serves to bias the latch lever 81 and the latch 89 to their latching positions.

A trip bar 95, extending across all of the poles of the breaker, is rigidly mounted on the right-hand end of the channel-shaped latch 89 and has insulating brackets 97 (only one being shown) secured thereto, there being a bracket 97 for each pole of the breaker. Each of the brackets 97 has a headed screw 99 adjustably mounted thereon for cooperating with the trip device 13 of its associated pole in a manner to be presently described.

The breaker is tripped open manually by means of a cam member 101 mounted on the inner end of a handle shaft 103 journaled in a bearing 105 mounted in the front piece of the frame 45. The handle is not shown in the drawings but is rigidly secured to the outer end o the shaft 103 and biased in both directions to a central position in a well known manner by means of a spring 107.

Rotation of the handle shaft 103 in tripping direction causes the cam member 101 to engage and actuate the latch member 89 in counterclockwise or unlatching direction to unlatch the intermediate latch lever 81, which, in turn, releases the main latch 77. This permits the tripping toggle 59-61 to collapse upwardly to effect opening of the breaker contacts. During the collapse of the tripping toggle a portion 109 of the toggle link 61 engages and actuates the support member 73 to a non-supporting position, thereby freeing the closing toggle 61-63. The closing toggle thereupon collapses downwardly and during its collapse resets and relatches the tripping toggle 59--61 The breaker contacts may now be operated to the closed position by rotating the shaft 103 and the cam 101 in the direction opposite to the tripping direction. This causes the cam 101 to engage a projection 111 on the closing toggle link 63 and moves this link counterclockwise about its pivot 67 until the support member 73 resumes its supporting position below the knee pivot pin 71. During the closing operation the link 79 prevents collapse of the tripping toggle 59--61 which acts as a thrust transmitting means and moves the movable contact structure to the closed position.

The breaker is automatically tripped open by operation of the trip device 13 for any pole of the breaker. The trip device includes generally a tripping electromagnet 113 (Figs. l and 2) and a time delay device 115. The tripping magnet 113 includes a C-shaped magnet yoke 117 comprising thin sheet-like laminations 119 bent llatwise and disposed in nested relation with each other. In order to form a rigid structure to provide a rigid support for the trip device 13 and the time delay device 115, the inner and outer laminations 121 of the magnet yoke are made considerably thicker than the center laminations 119. The ends of the laminations 121 are welded together as shown at 123 to form mounting feet for securing the magnet yoke to the insulating base 15. The ends 123 of the magnet yoke are drilled and tapped to receive mounting bolts 125 and 127 as shown in Fig. 1.

The stationary core, indicated generally at 129, comprises a thin sheet 131 of magnetic iron having its inner end welded to a tubular member 133 of magnetic material and spirally wound about the tubular member to form a cylindrical core member. The lower end of the tubular member is flanged as at 135 to form a support for the stationary core. The upper end of the tubular member 133 is provided with an internal thread which cooperates with a threaded nipple 137 disposed in an opening in the magnet yoke to rigidly secure the stationary core structure 129 to the magnet yoke and to rigidly secure the laminations together. The lower portions of the laminations 7, 119 and 121 are secured together by means of screws Surrounding the stationary core member 129 is an insulating tube 139 around which is disposed the energizing coil 141 of the magnet. As shown in Fig. l, the bolt 125 which secures the upper end of the magnet yoke to the base also secures the flexible conductor 39 to the upper turn of the coil141. The lower turn of the coil 141 is formed into a lug 143 which, together with the inner end 145 of a terminal 147 is secured to the base 15 by means of a bolt 149. A tubular member 151 (Fig. 3) of magnetic material is mounted in an opening in the lower portion of the magnetic yoke 117 and extends upwardly within the insulating tube 139. Disposed within the tubular member 151 is a movable core member or armature indicated generally at 153 comprising a cup-shaped upper portion 155 and a tubular lower portion 157 rigidly secured together by suitable means such as brazing. The portion 155 is provided with a central opening through which extends a sleeve 159 surrounding a trip rod 161 extending axially through the movable armature 153, the sleeve 159 and an opening in the nipple 137. A spring 163 coiled about the trip rod 161 is compressed between a eounterbore in the member 157 and the shouldered lower end of the sleeve 159. The upper end of the sleeve 159 is counterbored and engages a spring clip 165 seated in an annular groove in the trip rod 161.

The trip rod 161 is moved upwardly to trip the breaker under the control of the time delay device 115 which comprises, generally, a exible diaphragm 167 (Fig. 3) attached to the lower end of the trip rod and several valve elements for admitting air to the space below the diaphragm at various rates to provide different amounts of time delay. The flexible diaphragm is disposed in a chamber 169 formed in an upper housing member 171 and a lower housing member 173, both of said housing members being formed of molded insulating material. The outer edge of the diaphragm 167 is clamped between the housing members, together with a sealing gasket 175 to form an air-tight seal. The housing members 171-173 are secured together and rigidly secured to the magnet yoke 117 by means of bolts 177 (Fig. l) (only one of which is shown). The central portion of the diaphragm 167 is clamped between upper and lower clamp members 179 and 101, respectively, the upper clamp 179 having an annular projection 183 extending downwardly through an opening in the lower clamp 181 and formed over against the lower face of the latter to form an air-tight seal.

Secured to the lower end of the trip rod 161 is a sleeve 185 having a flange thereon brazed to the bottom face of the upper clamp 179. The lower portion 157 of the movable armature extends downwardly through an opening in the upper wall of the housing member 171 and is normally seated on the upper face of the upper clamp 179.

Since the spaces above and below the diaphragm 167 are completely sealed oft from each other and the space above the diaphragm is at atmospheric pressure, any force tending to raise the trip rod 161 will be restrained by the partial vacuum below the diaphragm. In order to control the rate of tripping movement of the trip rod 161, several valve devices are provided to admit air to the space below the diaphragm. The valve devices comprise a long-time delay valve indicated generally at 187 (Fig. 3), a short-time delay valve indicated generally at 189 (Fig. 2) and an instantaneous valve 191 (Fig. 3).

vThe long-time delay valve device 187 comprises a valve seat 193 molded integral with the bottom housing member 173, a tubular metal insert 195 molded in the housing member 173 surrounding the valve seat 193 and having an internal thread therein, a valve mem.- ber 197 cooperating with the valve seat 193 and threadedly engaging the tubular insert 195 whereby it may be adjusted and an insulating adjusting knob 199 supported on a ange 201 on the valve member 197. The air entering the space below the diaphragm is ltered by means ot a suitable filtering material 203 supported be tween an annular flange 205 on the knob 199 and a cooperating annular projection 207 formed integral with theV housing member 173. An air passage 209 in the form of a groove is provided along the threaded surface of the valve 197 and a passage 211 is provided axially through the valve seat 193. rl`he ow of air into the Y chamber below the diaphragm 167 is throughv the filter 203, the passage 209, the orifice defined by the valve 197 and the valve seat 193 and through the passage 211.

The knob 199 is provided with serrations (not shown) which engage corresponding serrations (also not shown) in the flange 201 of the valve 197 so that rotation of the knob also rotates the valve to vary the orifice and thereby vary the amount of time delay. The valve device 187 is calibrated by pushing upward on the knob 199 to disengage it from the valve member 197. The knob is then set to zero and the valve member rotated to closed position and the knob released. The knob is restored to engagement with the valve by means of a spring 213 compressed between the bottom of the housing 173 and the knob.

The short-time delay valve 189 (Fig. 2) controls a passage for admitting air from the space above the diaphragm 167 to the space below the diaphragm at a rate to provide for tripping the breaker with a very shorttime delay in the order by alternating current cycles. The valve device 189 comprises a tubular valve member 215 (Fig. 2) disposed in an opening 216 in the housing member 171 and having an enlarged head portion 217 seated in an opening in the housing member 173, the valve member 215 being held in position by a plug 219 screwed into the opening in the housing member 173. A valve 221 slidable in the tubular valve member 215 normally cooperates with a valve seat formed in the tubular valve member to close a communication with opposite sides of the diaphragm. The valve element 215 is provided with an axial passage in which is disposed a tapered projection 223 of the valve 221 and which is normally closed by the valve 221. A passage 225 (Fig. 2) in the housing member 171 communicates the chamber 169 above the diaphragm 167 with the space in the opening 216 above the valve seat. A passage 227 in the housing member 173 communicates the space below the diaphragm 167 with a horizontal passage 228 in the head 217 of the valve element 215 which passage 228 communicates with the axial passage in the valve member 215 that is normally closed by the valve 221. Thus opposite sides of the diaphragm 167 are communicated by the passage comprising passage 225, space 216 above the valve seat, the axial passage through valve member 215, passages 228 and 227. This passage is normally closed by the valve 221.

Upward or opening movement of the valve 2.21 opens the passage through the valve element 215 and establishes communication from the upper to the lower side of the diaphragm. The valve 221 is actuated to the open position by means of a valve operating armature 229 which is biased by means of a spring 231 to its unattracted position and is attracted upwardly by the tripping magnet 113 when this magnet is energized by overloads in the intermediate range of overloads of, for instance, 200% to l000% of normal rated current. The armature 229 is shown in Fig. 2 broken away, but is suitably pivotally mounted at its right-hand end. The magnet yoke 117 has an opening 233 therein and the inner laminations 119 extend downward thereunto substantially as shown in Fig. 2 to provide an air gap for operating the valve operating armature 229. A bracket 235 secured to the armature 229 engages under a head 237 on the valve 221 upon operation of the armature to actuate the valve to open position.

The rate of ow of air to the space below the diaphragm and consequently the rate of tripping movement of the trip rod 161 is controlled by the amount of opening of the valve 221. The opening movement of the valve 221 is adjustably controlled by means of an adjustable S- shaped stop member 239 (Fig. 2). The upper portion 241 of the S-shaped member comprises an adjustable stop and is disposed in the path of the upturned end of the armature to be engaged thereby and thus limit the upward movement of the armature 229 and limit the extent of opening of the valve 221. The center cross bar 243 of the S-sh'aped member has a threaded opening therein which is engaged by the reduced threaded portion 245 of an adjusting screw 247, so that upon rotation of the screw 247 the S-shaped member 239 will be moved up or down, depending upon the direction of rotation, to provide for greater or lesser movement of the armature 229 and, hence, greater or lesser opening movement of the valve 221.

The lower end of the adjusting screw 247 has a reduced uted portion molded into an insulating knob 249. The knob 249 is rotatably mounted in an insulating cross bar 251 secured to the underside of the housing member 173 by screws 253 only one of which is shown. A spring washer 255 seated in an annular groove in the adjusting screw 247 biases the screw upwardly and presses a ange on the knob 249 against the underside of the cross bar 251.

The adjusting screw 247 has an enlarged threaded portion 257 which passes through a clearance opening in the lower horizontal portion of the S-shaped member and threadedly engages a pointer 259. The lower vertical portion of the S-shaped member has cut-away portions on opposite edges thereof which are engaged by projection on the pointer 259 so that the latter will travel up and down without rotating. The outer end of the pointer 259 is reduced and extends through a vertical slot in an index plate 261 supported at its lower end on the cross bar 251 and having its upper end secured to a cross member 263 molded integral with side members 265, which in turn, are integral with the housing member 171.

The thread on the portion 257 of the adjusting screw has approximately twice the lead of the thread on the portion 245, hence, for one rotation of the adjusting screw the pointer 259 will move twice the distance as the S-shaped member 239. This makes possible an expanded dial on the index plate 261 and provides for more accurate setting of the short-time delay device.

The instantaneous valve device 191 (Fig. 3) is of the same construction as the short-time delay valve device with the exception that the tapered end which extends into the passage controlled thereby is omitted to permit instantaneous full opening of the passage permitting substantially unobstructed ow of air to the space below the diaphragm and instantaneous operation of the trip rod. Referring to Fig. 3, the instantaneous valve 191 is operated to the open position by means of an armature 267 similar to the armature 229 for the short-time delay valve. The armature 267 is provided with projections 269 (only one being shown) which pivotally support the right-hand end of the armature 267 in suitable recesses in the housing member 171. The armature 267 is biased to unattracted position by means of a spring 271 and when operated, a bracket 273 secured to the armature engages a head 275 on the Valve 191 and operates the valve to open position.

The main movable core member 153 (Fig. 3) is biased to unattracted position by means of a pair of springs 277 (only one being shown) having one end attached to a member 279. One end of the member 279 is pivotally supported in notched studs 281 (only one being shown) and the other end of the member 279 is provided with inwardly extending projections 283 (only one being shown) which engage in an annular groove 285 in the tubular member 157 of the movable core. The other ends of the springs 271 are attached to a pointer 287 which is threadedly engaged by an adjusting screw 289 rotatably mounted in the cross member 251 and having an adjusting knob 291 secured to the lower end thereof below the cross member. The pointer 287 is provided with a reduced portion extending through a vertical slot in the index plate to prevent rotation of the pointer when the adjusting screw is turned and to indicate the setting of the spring adjustment.

The springs 231 (Fig. 2) and 271 (Fig. 3) for the short-time delay valve armature 229 and the instantaneous valve armature 267 are attached to pointers like the pointer 287 (Fig. 3) and are provided with adjusting screws and knobs like those associated with the main movable core member. By adjusting the tension of the springs 277, 231 and 271, the pick-up point or the amount of overload current required to operate the associated armatures may be varied. That is, the pick-up point for longtime delay tripping, short-time delay tripping and instantaneous tripping may be varied.

The trip device operates with time delays of different durations in two distinct `ranges of overcurrents below a predetermined magnitude, and instantaneously in response to overcurrents above the predetermined magnitude, or in response to short-circuit currents. The ranges of overcurrents may be arbitrarily dened as, for example, a low range up to 500% or 600% of normal rated current, an intermediate range between 500% or 600% and 1000% of normal rated current, and instantaneous l000% or more of normal rated current.

Assuming an overcurrent within the low range of over currents, the trip device will operate as follows: upon the occurrence of an overcurrent in the low range the tripping electromagnet becomes energized and attracts the armature 153 upwardly. The armature acts through the spring 163 and the sleeve 159 to produce an upward thrust on the trip rod 161, the movement of the trip rod being retarded by the partial vacuum below the diaphragm 167. The trip rod 161 moves slowly upwardly in tripping direction as air is drawn into the space below the diaphragm through the longtime delay valve 187 until the upper end of the trip rod engages the headed screw 99 (Fig. l) and actuates the latch mechanism to effect tripping of the breaker in the manner previously described. The time delay provided by the long-time delay device 187 is in the order of seconds and may be varied by adjusting the valve 193-197 as set forth previously.

As soon as the breaker contacts are opened the tripping magnet 113 is deenergized, and the armature 153 and the trip rod are restored by the springs 277 and the force of gravity to the Fig. 3 position. A spring-biased by-pass valve 293 (Fig. 3) controls a passage through the diaphragm 167 to provide for quick restoration of the armature 153, the trip rod 161 and the diaphragm 167 to their normal positions following a tripping operation.

When an overcurrent in the intermediate range ot overcurrents occurs, the electromagnet 113 is energized suiiiciently to attract the shorttime delay armature 229 (Fig. 2) upwardly against the adjustable stop 241 opening the short-time delay valve 189 an amount determined by the adjustment of the stop 241. T his admits air to the space below the diaphragm 167 at a higher rate than the longtime delay valve and provides a relatively short-time delay in the order of alternating current cycles in the tripping operation.

Energization of the tripping magnet 113 in response to an overcurrent in the intermediate range is not suflicient to attract the armature 267 (Fig. 3) for the instantaneous valve 191, however, upon the occurrence of an overcurrent of 1000% or more of rated current, both the short-time delay armature 229 (Fig. 2) and the instantaneous armature 267 (Fig. 3) are attracted and open both the shorttime delay valve 189 (Fig. 2) and the instantaneous valve 191 (Fig. 3), thereby admitting air to the space below the diaphragm 167 at a rate suicient to permit substantially instantaneous tripping movement of the trip rod.

On short-.time delay and instantaneous tripping operations, the spring 163 limits the force applied by the moving armature 153 to the time delay device. On such operations the armature 153 is attracted immediately against the fixed core member 129 compressing the spring 16.3 which then supplies the force necessary to actuate the trip rod. Thus the pull exerted in the time delay device is limited to the maximum force exerted by the spring 163 when it is compressed. Thisprevents damage to the time delay device and'also provides a uniform pull on the time delay device.

XVe claim as our invention:

l. ln a circuit breaker, the combination of a trip device operable to effect an automatic operation comprising a trip member, electromagnetic means for operating said trip member including, a fixed core member, a shaped mag-V net yoke comprising a group of relatively thin substantially coextensive sheets of magnetic material, said sheets of magnetic material being disposed peripherally of said C- shaped magnet yoke and parallel thereto, a pair of rigid members substantially coextensive with said sheets disposed one on each vside of said group of Sheets and in close proximity thereto, said sheets together with said rigid members being bent atwise and disposed in nested reia tion to form said @l-shaped magnet yoke, said magnet yoke having one leg portion extending from one end of said xed core member, another leg portion extending parallel to the axis of said fixed core member and a third leg portion extending across the other end of said magnet, said group of sheets and said rigid members being disposed and arranged to form a rigid support for said trip device, said fixed core member being mounted Within said C- shaped magnet yoke on said one leg portion thereof, an energizing winding surrounding said fixed core member between said one leg portion and said third leg portion of said magnet yoke, a movable core member having a portion extending into said Winding adjacent said third leg portion ot said C-shaped magnet yoke and operable upon energization of said electromagnetic means in response to overload currents to actuate said trip member, time delay means comprising a fluid dashpot for retard ing operation of said trip member, valve means for ad mitting vfluid to said dashpot to eect a predetermined time delay in the operation of said trip member, a valve operating armature disposed adjacent said third leg portion ot said C-shaped magnet yoke operable upon energization of said electromagnetic means in response to overload currents of predetermined value to operate said valve means, and said third leg portion of said C-shaped magnet yoke having an opening therein adjacent said valve operating armature providing an air gap for effecting operation of said valve operating armature.

2. In a circuit breaker, the combination of a trip device comprising a trip member, electromagnetic means for operating said trip member including, a fixed core member, a C-shaped magnet yoke comprising a plurality of relatively thin substantially coextensive sheets of magnetic material disposed peripherally of said C-shaped magnetic yoke and parallel thereto, a pair of rigid members substantially coextensive with said sheets disposed one on each side of said sheets in close proximity thereto, said sheets together with said rigid members being bent fiatwise and disposed in nested relation to form said C-shaped magnet yoke, said magnet yoke having one ieg portion extending from one end of said fixed core member, another leg portion extending parallel to the axis oi said fixed core member and a third leg portion extending across the other end of said magnet, said rigid members being secured together with said sheets between them to form a rigid support for said trip device, said fixed core member comprising a tubular member disposed Within said C- shaped magnet yoke and having a relatively thin sheet of magnetic material coiled spirally thereon, said tubular member being rigidly secured to said one leg portion of said C-shaped magnet yoke, an energizing winding surrounding said xed core member, a movable core member disposed in axial alignment with said iixed core member adjacent said third leg portion of said C-shaped magnet yoke and operable upon energization ot said electromagnetic means in response to overload currents to actuate said trip member, time deiay means comprising a fluid dashpot for retarding operation of said trip member, valve means for admitting iiuid to said dashpot to effect a predetermined time delay in the operation ot' said trip member, a valve operating armature disposed adjacent said third leg portion operable upon energization of said electromagnetic means in response to overload currents 0f predetermined value to operate said Valve means, said C- shaped magnet yoke having an opening in said third leg portion thereof adjacent said valve operating amature providing an air gap for effecting operation of said valve operating armature.

3. An electroresponsive device including a fixed core member, a C-shaped magnet yoke comprising a group of relatively thin substantially coextensive sheets of magnetic material disposed peripherally of said `C-shaped magnet yoke and parallel thereto, a pair of rigid members substantially coextensive with said sheets disposed one on each side of said groups of sheets and disposed and arranged to form a rigid unitary support for said device, said sheets together with said rigid members being bent atvvise and disposed in nested relation to form said C- shaped magnet yoke, said magnet yoke having one leg portion extending from one end of said fixed core member, another leg portion extending parallel to the axis of said fixed core member and a third leg portion extending across the other end of said magnet, said fixed core member comprising a tubular member disposed within said C-shaped magnet yoke and rigidly secured to said one leg portion of said magnet yoke, said tubular member having a relatively thin sheet of magnetic material coiled spirally thereon, an energizing Winding coiled about said fixed core member, and an armature disposed within said Winding adjacent said third leg portion of said C-shaped magnet yoke and actuated upon energization of said Winding.

4. An electroresponsive device including a stationary core member, a `C-shaped laminated magnet yoke comprising a plurality of relatively thin substantially coextensive sheets of magnetic material disposed in close proximity to one another, said sheets being arranged peripherally of said C-shaped magnet yoke and parallel thereto, at least one of said sheets being of substantially greater thickness than the other sheets, said sheets being disposed and arranged to form a rigid support for said device, said sheets together with said rigid members being bent flatwise and disposed in nested relation to form said C-shaped magnet yoke, said magnet yoke having one leg portion extending from one end of said fixed core member, another leg portion extending parallel to the axis of said fixed core member and a third leg portion extending across the other end of said magnet, said stationary core being disposed Within said magnet yoke and comprising a tubular member rigidly secured to said one leg portion of said magnet yoke and having its axis disposed at right angles to said one leg portion, a relatively thin sheet of magnetic material having one end secured to said tubular member and coiled spirally about said tubular member, an energizing winding surrounding said fixed core member, and a movable core member disposed in said Winding adjacent said third leg portion of said magnet yoke and movable upon energization of said winding.

5. In a circuit breaker, an electromagnetic trip device comprising a fixed core member, an energizing winding surrounding said fixed core member, a laminated C-shaped magnet yoke comprising a plurality of substantially coextensive sheets of magnetic material bent fiatwise and disposed in nested relation to form said C-shaped magnet yoke, at least one of said sheets being of substantially greater thickness than the other sheets, said sheets being secured together to form a rigid support for said trip device, said lC-shaped magnet yoke having a leg portion extending from one end of said fixed core member, another leg portion extending parallel to the axis of said fixed core member and a third leg portion extending across the other end of said magnet, said fixed core member being disposed within said magnet yoke and mounted on the first mentioned leg portion, and a movable core member having a portion extending into said Winding adjacent said third leg portion and movahie upon energization of said electromagnet in response to overload currents.

6. In a circuit breaker, an electromagnetic trip device comprising a fixed tubular core member, an energizing Winding surrounding said fixed core member, a laminated C-shaped magnet yoke comprising a plurality of substantially coextensive sheets of magnetic material bent fiatwise and disposed in nested relation to form said C-shaped magnet yoke, at least one of said sheets being of substantially greater thickness than the other sheets, said sheets being secured together to form a rigid support for said trip device, said C-shaped magnet yoke having a leg portion extending from one end of said tubular core member, another leg portion extending parallel to the axis of said tubular core member and a third leg portion extending across the other end of said magnet, said fixed tubular core member being disposed Within said magnet yoke and secured to said first mentioned leg portion, and a movable core member having a portion extending into said winding adjacent said third leg and movable by energization of said electromagnet in response to overload currents.

7. In a circuit breaker, an electromagnetic trip device comprising a fixed core member, an energizing Winding, a C-shaped magnet yoke comprising a pair of spaced rigid members bent fiatwise in C-shape, a plurality of relatively thin sheets of magnetic material bent atwise and disposed between said rigid members in nested relation with each other and with said rigid members, said C-shaped magnet yoke having a leg portion extending from one end of said fixed core member, another leg portion extending parallel to the axis of said fixed core member and a third leg portion extending across the other end of said magnet, said fixed core member being disposed between said one leg portion and said third leg portion of said magnet yoke and mounted on the first mentioned leg portion, a movable core member having a portion extending Within said third leg portion and disposed in axial alignment with said fixed core member, said energizing Winding surrounding said fixed core member and said portion of said movable core member.

8. An electroresponsive device comprising a fixed tubular core member, a movable core member in axial alignment with said fixed core, a C-shaped magnet yoke comprising a plurality of relatively thin substantially coextensive sheets of magnetic material, a pair of rigid magnetic members substantially coextensive with said sheets disposed one on each side of said sheets, said sheets and said rigid members being bent flatwise and disposed in nested relation to form said C-shaped magnet yoke, said magnet yoke having one leg portion extending from one end of said fixed tubular core member, another leg portion extending parallel to the axis of said fixed and movable core members, and a third leg portion extending across the other end of said magnet, said fixed tubular core member being rigidly secured to said one leg portion of said magnet yoke and extending toward said third leg portion, a relatively thin sheet of magnetic material coiled spirally about said tubular core member, and an energizing winding disposed between said one leg and said third leg of said magnet yoke and coiled about said fixed core member.

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